I have a way to do this: I have a smartphone without an unlimited data plan. I can use it out of the home for calls, texts, notes, photos, music, and cached maps, without being tempted to surf the web or whatever. If I need a map or a web browser urgently, I can still use data, but I pay a relatively high rate for it. I call this a "self-imposed vice tax".

Of course, on wifi, it can do everything that phone with a normal data plan can do. I just don't bother, because most of the time I'm on wifi, I have a laptop available. Especially these days.